The novel compounds of the invention, 12'-hydroxyverrucarin J, as represented by the structure in FIG. 1 and iso-satratoxin H, as represented by the structure in FIG. 2, are members of the trichothecene family of antibiotics, a review of which can be found in "Progress in the Chemistry of Natural Products," 31: 64-117 (1974), by C. Tamm. 12'-Hydroxyverrucarin J is a novel compound that can be readily distinguished from all other reported trichothecenes by, among other features, the presence of a signal in the proton nuclear magnetic resonance spectrum (pmr) in CDCl.sub.3 at 0.64 parts per million (ppm) downfield from tetramethylsilane (TMS) standard and the absence of the characteristics methyl singlet at .about.2.3 ppm in verrucarin J and other trichothecenes having a 2'-double bond. Iso-satratoxin H is a novel stereoisomer of satratoxin H. The latter compound was reported by R. M. Eppley, E. P. Mazzola, R. J. Highet, and W. J. Bailey, J. Org. Chem. 42: 240 (1977). Iso-satratoxin H is clearly distinguished from satratoxin H by, among other features, the presence of a signal in the proton nuclear resonance spectrum in CDCl.sub.3 at 4.22 ppm downfield from TMS. No stereoisomers of satratoxin H have been reported in the chemical literature nor has a patent on any such stereoisomer been found to exist. The above properties, in addition to other properties described hereinafter, clearly establish 12'-hydroxyverrucarin J and iso-satratoxin H as novel trichothecenes. These compounds exhibit antimicrobial and antitumor properties when tested by standard procedures.